RESUMEN
Objective To study the stress on elastic substrate of an in vitro endothelial cell dynamic culture device, whose hemodynamic environment is designed to simulate the human body, and to test and observe the shear stress changes in elastic substrate of parallel plate flow chamber under different tensile stresses. Methods A series of static tensile tests were adopted to fit the condition of dynamic stretching. Namely, the silicone sheet with 2 different thicknesses were put into the device, and then applied with static stretch at the interval of 10% tensile rate (0%, 10%, 20%, 30%), and under the condition of maintaining its tensile rate, the chamber height after the stretch of silicon sheet was calculated. Based on the calculation of shear stress, shear stress curves at different tensile rates were obtained, to make comparative analysis on variation of the shear stress with the thickness of silicon sheet. Results The experimental result was consistent with the theoretical analysis. When the tensile rate was 30%, silicon sheet with 0.5 mm thickness would produce certain influence on shear stress of parallel plate flow chamber along with the change of tensile rate (the height of chamber), and the average and maximum shear stress were reduced by 10.1% and 10.4%, respectively. Conclusions The influence factors caused by the change of elastic substrate thickness after the introduction of tensile stress must be taken into account for the calculation of shear stress in parallel plate flow chamber. The result can provide experimental technology for the culture of endothelial cells in vitro and the design and development of novel parallel plate flow chamber.
RESUMEN
BACKGROUND:After years of development, various in vitro loading devices for vascular tension stress have been created both at home and abroad, mainly including rectangular base stretching method, circular base deformation method and four-point bending beam load method. Although the circular base deformation method can wel reflect the real situations in vivo such as the expansion of the alveoli and vascular pulsation, the strain on the membrane is actinomorphic. The four-point bending beam load method can just bring limited strain range and load time, along with a difficult strain regulation. OBJECTIVE: To develop anin vitro loading device for vascular tension stress using the rectangular base stretching method. METHODS:Thisin vitro loading device for vascular tension stress developed according to mechatronics design consisted of power supply module, control module, drive module and data acquisition module. The device could achieve the tensile control on silicon diaphragm by high-precision control of the motor rotation angle and rotational speed. RESULTS AND CONCLUSION: Through tests and experiments, the device could meet the required range of parameters and simulatein vitro human tensile stress environment, which is preliminarily considered to develop successfuly, achieving that: (1) two work patterns: stress mode and strain mode so as to solve the standardization of silicone substrate as loading device; (2) tensile stress can be adjusted in a range of 0-5×105 Pa; (3) tensile strain can be adjusted in 0-40% range; (4) stretching frequency can be in the regulation of 0-80 times/min and the stretching time can be controled.
RESUMEN
<p><b>OBJECTIVE</b>To explore the value of preoperative evaluation with three-dimensional endoanal ultrasonography (3D-EAUS) for anal fistula in order to provide preoperative assessment for anal fistula.</p><p><b>METHODS</b>One hundred patients diagnosed with anal fistula undergoing surgery between March 2012 and March 2013 in our department were prospectively enrolled. All the patients were randomly divided into the ultrasound group and the control group with fifty patients in each group. The ultrasound group received 3D-EAUS and the control group received routine examinations (digital examination and probe) to assess the position of the internal opening, the type of fistula and secondary tracks, respectively. The concordance rate of the preoperative assessment and intraoperative exploration was evaluated between the two groups.</p><p><b>RESULTS</b>The accuracy of identifying internal opening was 96.0% for the ultrasound group and 82.0% for the control group with statistically significant difference (P=0.02). The accuracy of identifying internal opening for simple anal fistula was similar (95.0% vs. 91.3%, P=1). For complex anal fistula, the accuracy was also higher in the ultrasound group (96.7% vs. 74.1%, P=0.025). The accuracy of fistula classification was 78.0% for the ultrasound group and 96.0% for the control group with significant difference (P=0.01). The accuracy of identifying a second track was higher in the ultrasound group (96.0% vs. 82.0%, P=0.025).</p><p><b>CONCLUSIONS</b>It is significantly superior for 3D-EAUS to detect the internal opening, fistula classification and identification of a second track in complex anal fistulas as compared to conventional examination. 3D-EAUS should be recommended as a preoperative assessment for anal fistula, especially for complex one.</p>